Stage light fixtures are known, which are provided with a light source adapted to emit a light beam along an optical axis and with at least one diaphragm arranged along the optical axis for intercepting the light beam. The stage light fixtures of this type are also generally provided with a zoom assembly arranged downstream of the diaphragm along the optical axis. Therefore, in the stage light fixtures of this type, the zoom assembly is arranged so as to intercept the beam after the beam has crossed the diaphragm and is configured to enlarge or reduce the dimensions of the projected beam.
However, the stage light fixtures of this type emit a light beam characterized by a luminosity which decreases as the distance at which the beam is to be projected increases. In such stage light fixtures, the luminosity cannot be changed and thus, preventing the loss of luminosity is not possible.